The present disclosure relates to turbine engines, and more particularly, to a system for simulating flow through a fuel system of a turbine engine that operates on either gaseous or liquid fuel.
Turbine engines may be used to generate electrical power by burning the fuel to rotate the turbine blades. The basic principles and operation of turbine engines are generally well understood: a gas combustion engine attached to rotors of the turbine coverts the chemical energy of combusting fuel into mechanical energy to rotate the rotors, and the rotors in turn spin a magnetic around a coil of wire to induce an electrical current in attached wires. Modern power plants often use dual-fuel turbine engines, which typically use gaseous fuel, such as natural gas, as a first fuel and liquid fuel, such as liquid petroleum, as a second fuel. One or both fuels may be supplied to the engine by separate pipelines. A fuel control system segregates the first and second fuels and regulates their supply to the engine.
In a power plant, typically the dual-fuel turbine engine will operate for very long periods of time using the gas fuel as it is supplied from a natural repository. For example, natural gas may be transported from a gas mine via the pipeline directly to the turbine engine. In such applications, the liquid fuel is used only in certain infrequent situations, such as emergency, power-up, power-down, or gas fuel system maintenance situations. The liquid fuel system components may deteriorate while unused due to the cumulative effects of heat, coking, water entrainment, and corrosion. In a particular example, coke can solidify on the surfaces of pipes, valves, and seals that are in high-temperature locations and experience prolonged heating above about 250 degrees Fahrenheit.
When the liquid fuel system is activated, compromised components are likely to cause fuel delivery problems, fuel contamination, temperature variability, and ultimately damage or forced shutdown of the turbine. These problems are widely recognized and may contribute to significant losses in productivity and repair and operational costs. Turbine operators attempt to mitigate degradation and ascertain the functionality of the liquid fuel systems by periodically operating the turbine on liquid fuel through its “startup” and “run” stages to test for problems. This approach has several major drawbacks. Primarily, the turbine must be powered down and switched from gas to liquid fuel. This can cause lost productivity. Furthermore, as the turbine engine cools during power-down, components in the casing surrounding the turbine blades may heat or cool faster than each other or than the blades, distending the casing or otherwise reducing the clearance gap between the casing and the blades to the point that a blade tip impact could occur, resulting in costly damage and potential injury to workers.
In any event, the turbine is actually “fired” during the test, meaning the liquid fuel system is operated at its full capacity from fuel source to fuel combustion. If there are problems in the fuel system, the test could damage the turbine. Moreover, the firing of the liquid fuel system causes unwanted emissions. The emissions may be in the form of lost fuel, which is burned in the test even if the liquid fuel system is operating normally, or in the form of byproducts of burning the fuel. Thus, the test results in resource costs and could potentially violate emissions rules and cause fines or other penalties to be levied against the plant.
A need exists for a test environment for liquid fuel systems of dual-fuel turbine engines that does not burn the liquid fuel and does not require the turbine to be powered down for testing.